Аn original approach to find a maximum-size independent set in a fuzzy graph is presented together
with the necessary formalization technique. The approach is oriented at practical usage in
applied artificial intelligent systems using fuzzy logic and modal logic concepts. The problem may
be encountered in face recognition with some possible distortions. The vertices stand for the points
in the face image with approximately similar color and brightness. Obviously, in the case of image
distortion the arcs in the graph may be assigned with the values in 0,1‑diapason. A fuzzy graph contains
some nodes (arcs) with indefinite measure of their belonging to the graph. The situation may
appear when no constrict classifying rules exist as explained in the paper. One can use a measure
of 0.5 to interpret indefiniteness. This an interpretation enables one to apply modal logic for problem
formalization and solving. The modality of the type «possible» is interpreted by the 3‑valued formula
with truth value not less than 0.5; the modality of the type «necessary» is interpreted by the 3‑valued
formula with the truth value equal to 1. The approach represented in the paper may be interesting
for the researchers engaged in the recognition and classifying problems.